As would be understood by one of skill in the art, a pipette is a device that is normally used in conjunction with a pipette tip to transfer or distribute a measured volume of liquid from one location to another. Manually-operated air-displacement pipettes, which are of the most interest with respect to this application, operate generally by creating a vacuum via the retraction of a piston located in the pipette body. Thus, when the open end of an associated pipette tip is submersed in a liquid, the resulting vacuum draws air from the pipette tip and an amount of the liquid is consequently drawn into the tip to replace the evacuated air. Movement of the pipette piston is regulated such that a desired measured amount of liquid is drawn into the tip during the aspiration phase of the pipetting operation.
Manually-operated air-displacement pipettes are available in a wide volume range of between about 0.24 to several thousand μL. Because a user may need to pipette a multitude of different liquid volumes, such pipettes are frequently offered with different volume ranges (e.g., 0.5-10 μL, 10-115 μL, 115-1,000 μL) and with volume adjustability within the selected volume range. Volume adjustability is commonly accomplished, for example, by manually rotating a provided volume setting shaft or manually rotating the plunger button and associated plunger of the pipette which, through one of various possible associated mechanisms, results in a change in the volume setting of the pipette.
A common drawback to known volume-adjustable pipettes has been the time and effort required to make volume adjustments—particularly when the difference between the current volume setting and a desired volume setting is large. For example, in the case of known volume-adjustable pipettes, a full rotation of the pipette volume adjusting device may result in a volume change of only 5%-10% of the total volume of the pipette. Thus, making a large change in volume may require significant and time consuming effort on the part of a user.
Volume adjustable pipettes with speed-increased volume adjustment functionality are known. However, these know pipettes suffer from various deficiencies including, but not limited to, complex and/or inaccurate volume adjustment mechanisms, the need to employ separate volume adjustment inputs for low speed and high speed volume adjustment; and/or the need to provide a volume adjustment input that is separate from the pipette plunger rod or plunger button.
As would also be understood by one of skill in the art, calibration of the dispensed fluid volume is required for accurate pipetting. Consequently, pipettes are typically calibrated at the factory and may also be calibrated during servicing operations.
In one known pipette design, calibration is accomplished by disconnecting a volume display from an associated volume screw, and volume offset is separately accomplished by moving a bottom stop. In another known pipette design, calibration is accomplished by disengaging a volume display from an associated volume screw using a spline-type coupling located within the counter wheels of the volume display, and subsequently adjusting the position of the volume screw. In yet another known pipette design, calibration and volume offset are accomplished by moving an upper stop of the pipette without changing the pipette volume display.
It is evident from the foregoing description that adjustable volume pipettes and pipettes that permit user calibration or volume offset are known. However, when the identified drawbacks of known volume-adjustable pipettes are considered in the context of the numerous pipetting operations and associated volume adjustments made by many pipette users over the course of a typical work day, the benefits of providing an improved design that facilitates more efficient pipette volume adjustment should be readily apparent. Similarly, while mechanisms and techniques for pipette calibration and volume offset are known, it would nonetheless be desirable to provide a simplified and compact pipette calibration/volume offset mechanism that may be used in conjunction with an improved pipette volume adjustment mechanism in a new manually operated pipette.